1. Field of the Invention
This invention relates generally to conveyor belt rollers, and more particularly, to a novel roller having double helix pattern tracks extending respectively left and right from the midpoint of the roller.
2. Description of the Prior Art
A common problem in use of conveyor belt systems such as for handling and moving luggage at airports, or the like, is the need for proper tracking and alignment of the conveyor belts during use. Conveyor belts have a tendency to drift or move from side to side during operation. Also, it is difficult to align a belt centrally upon the conveyor system rollers when the same initially is installed, or after replacement of a worn belt. A conveyor belt that drifts or wanders from the rollers on which it is mounted during use is subject to excessive wearing of the edges of the belt, and even tearing if the belt catches on or runs against frame parts or other support members of the conveyor system. This results in undesirable down time of the conveyor system for replacement of the worn belt. Initial and continuous centering of a belt when positioned upon conveyor rollers therefore is desired to be achieved quickly upon installation and continuously during operation of the conveying system to prevent excessive wearing and damage to the belt and optimum operating efficiency of a conveyor belt system.
Additionally, it is desirable for the conveyor rollers to have significant gripping traction against the underside of the belt to prevent slipping as the belt is moved upon the rollers. At low speed operation of a conveying system, traction is more easy to maintain than at higher speed operation. Prior art conveyor system speeds often must be maintained at relevantly low rates in order to prevent slipping which occurs at more desirable, higher speed operation.
Further, it is desirable to have a conveyor belt system in which the underside of the belt is kept relatively free of grease, oil, dirt and other debris which has a tendency to built up during operation, resulting in slipping of the belt over its rollers.
It is known in the art to provide conveyor belt rollers with helix pattern tracks which spiral around the roller surface a plurality of times so as to provide said surface with a pair of screw thread-like formations extending substantially the full length of the roller. The prior art rollers having such helix pattern tracks however, include a single left and single right thread only. For many years, such rollers with single right and single left helix threads have been used in conventional conveyor roller systems. The following U.S. patents disclose rollers having such single left and single right helix pattern threads:
______________________________________ 685,680 3,831,243 2,707,403 3,859,865 2,743,810 3,860,780 3,713,348 3,888,131 3,772,931 3,972,414 3,812,732 4,068,789 4,140,216 ______________________________________
The single helix thread pattern rollers of the prior art long have been felt to provide the maximum efficiency attainable for desired tracking and alignment centering and cleaning of conveyor belts during operation.
The roller of the present invention incorporates a respective double helix pattern track running left and right from the midpoint of the roller resulting in a roller having remarkably improved efficiency during initial and continuous high speed operation for better gripping, centering and cleaning of the conveyor belt driven by the roller. It has been ascertained that the double helix pattern tracks of the invention yield dramatic and unexpected increased drive and alignment characteristics over that which normally would be expected. The present invention provides a roller which aligns and centers the belt positioned thereon in substantially less time than that required during use of prior art rollers, resulting in significant maintenance and cost savings and reducing the amount of down time of conveyor systems. The roller with improved helix pattern of the invention also provides for significantly increased frictional gripping characteristics which enables conveyor systems using the roller to be run at greater speeds than those permissible with prior art rollers. Additionally, the double left and double right helix pattern tracks of the invention provide a roller having improved cleaning action on the underside of the belt positioned thereon so that grease, oil and debris are carried away from the underside of the belt more efficiently than in use of prior art rollers.
It is known in the art to provide conveyor rollers with shaft members upon which the rollers are fixed for rotative movement. In instances where such shafts are permanently affixed to the roller, the entire shaft and roller assembly must be removed for replacement even if only a part fails. Also, conveyor system rollers are used both for driving the conveyor belt and as idler rollers at additional locations along the conveyor system. Drive rollers are provided with shaft housings on the ends thereof with engagement means for transferring driving motion from the shaft to the roller. Idler rollers are provided with bearing housings on the ends thereof to permit free wheeling of the roller as the belt moves thereover. Interchangeability of bearing and shaft housings is a desirable feature to permit rollers to be interchanged upon a conveyor belt system for repair or replacement thereof, as necessary.